Breather device, liquid tank, and exhaust gas purifying apparatus to be adapted for engine

ABSTRACT

A breather device A 1  for pressure relief includes a breather pipe  121  serving as a fixing part, and an inner pipe  122  serving as a communication part and is provided by the breather pipe  121  with fixation strength enough for securing the breather device A 1  to a liquid tank  101 . The inner pipe  122  has a vent hole P formed therein for provide fluid-communication between the inside of the liquid tank  101  and the outside thereof in a manner such that an inner surface forming the vent hole P is made of a resin.

This application is a continuation of U.S. patent application Ser. No.12/240,843, filed on Sep. 29, 2008, which is a continuation ofPCT/JP2007/052679, filed on Feb. 15, 2007, both of which are herebyincorporated by reference in their entirety for all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a breather device, a liquid tank, andan exhaust gas purifying apparatus that is adapted for purifying exhaustgas from an engine. In particular, the present invention relates to atechnology for enabling it to prevent urea precipitation inside abreather device provided for a liquid tank in which urea aqueoussolution is stored.

2. Description of the Related Art

As a technology that has been developed for purifying nitrogen oxides(hereunder, referred to as NOx) exhausted from a diesel engine, by usingafter treatment, the urea SCR (Selective Catalytic Reduction) is known.This urea SCR adds ammonia to exhaust gas, and with this ammonia as areducing agent, reduces and purifies the NOx. In order to accelerate theNOx reduction, a reducing catalytic converter is disposed in the exhaustgas passage. In consideration of storage convenience, urea serving as anammonia precursor, is stored in a tank in an aqueous solution state, andin actual operation, the urea aqueous solution is supplied from thistank and injected into the exhaust gas passage upstream of the reducingcatalytic converter (Japanese Laid-open (Kokai) Patent ApplicationPublication No. 2000-027627, Paragraph No. 0013). The technology usingthis urea SCR is applied to exhaust gas purification in a diesel enginemounted on a large vehicle such as truck, and is being put to practicaluse.

Here, in the tank for storing the urea aqueous solution, in addition toa supply pipe for supplying the stored urea aqueous solution to a feedpump, there is provided a breather pipe for relieving pressure insidethe tank. By introducing atmospheric air through this breather pipe whensupplying the urea aqueous solution, the pressure inside the tank can bekept constant.

However, in this tank having the breather pipe, there is a problem inthat if the tank vibrates due to vibrations transmitted from the engine,or traveling on a corrugated road or the like, and sloshing occurs inthe stored urea aqueous solution, so that the urea aqueous solutionflows along the inner wall of the tank, or splashes, and consequentlyattaches to the breather pipe. If the attached urea aqueous solution isleft attached, this urea aqueous solution dries out due to contact withair from outside, causing precipitation of the urea, and with furtherrepeated attachment and precipitation, the precipitated urea isaccumulated, to thereby partially or completely clog the breather pipeinterior. It may be considered to attach a cover provided with a venthole in the vicinity of an opening of the breather pipe, to preventattachment of the urea aqueous solution to the breather pipe. However,in spite of provision of the cover, if the urea aqueous solution wereactually attached to the breather pipe, precipitation of urea from thisurea aqueous solution could not be avoided. Moreover, when, for example,stainless steel is adopted for the material of the breather pipe owingto the necessity to have sufficient endurance with respect to the ureaaqueous solution, the attached urea aqueous solution to the breatherpipe flows along the seam welded part thereof that is formed whenjoining the stainless steel material in a cylindrical shape by theconventional induction welding, so that the urea aqueous solution isconcentrated at the end of the seam welded part, with the result thatblockage caused by precipitation is promoted. This is not limited to atank for storing urea aqueous solution, but also in a liquid tank ingeneral, if liquid attached to the breather pipe is left attached,smooth introduction of atmospheric air through the breather pipe isobstructed.

SUMMARY OF THE INVENTION

For the above reasons, in a breather device for pressure relief providedin a liquid tank, it is preferable to return the attached liquidsmoothly into the liquid tank to avoid adverse effects caused by thisliquid being left attached.

The present invention provides a breather device, a liquid tank, and anexhaust gas purifying apparatus for an engine that addresses theabove-described problems.

The breather device of a liquid tank according to the present inventionis a breather device provided in a liquid tank for pressure relief. Thebreather device includes a fixing part that provides fixation strengthof the breather device to a liquid tank; and a communication part joinedto the fixing part. The communication part forms a vent hole of thebreather device for communication between the liquid tank interior andthe outside, and in the communication part, an inner surface of the venthole is formed from a resin.

The liquid tank according to the present invention includes a tank mainbody that forms a liquid storage part, and the aforementioned breatherdevice attached to the tank main body.

Moreover, the exhaust gas purifying apparatus for an engine according tothe present invention includes a liquid tank provided with theaforementioned breather device, and adds an aqueous solution of ammoniaor its precursor stored in the liquid tank to exhaust gas upstream of areducing catalytic converter provided in an exhaust gas passage.

According to the present invention, in the communication part of thebreather device, the inner surface of the vent hole is formed from aresin. As a result even if sloshing occurs in the liquid inside theliquid tank due to vibrations or the like, and the liquid becomesattached to the breather device, the liquid can be smoothly returnedinto the liquid tank. Therefore, when a urea aqueous solution is storedin the liquid tank, precipitation of urea due to urea aqueous solutionattached to the breather device being left attached can be avoided, andthe intrinsic pressure-relief function of the breather device can befavorably maintained. Furthermore, in a liquid tank in general, sincethe liquid attached to the breather device can be smoothly returned intothe liquid tank, interference with the smooth introduction ofatmospheric air through the breather device can be avoided.

Other objects and features of the present invention can be understoodfrom the following description, with reference to the appended drawings.

The entire contents of Japanese Patent Application No. 2006-098568, apriority of which is claimed, are incorporated as a part of the presentapplication herein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating a configuration of an exhaustgas purifying apparatus for an engine, according to a first embodimentof the present invention;

FIG. 2 is a plan view of a liquid tank according to the aboveembodiment.

FIG. 3 is a side view of the liquid tank.

FIG. 4 is an enlarged sectional view of a lid part of the liquid tank.

FIG. 5 is a cross-sectional view illustrating a configuration of abreather device according to the above embodiment of the presentinvention.

FIG. 6 is a schematic front elevation view illustrating an inner pipethat serves as a communication part of the breather device.

FIG. 7 is a cross-sectional view illustrating a configuration of abreather device according to a second embodiment of the presentinvention.

FIG. 8 is a cross-sectional view illustrating a configuration of abreather device according to a third embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereunder, is a description of embodiments of the present invention,with reference to the accompanying drawings.

FIG. 1 shows a configuration of an exhaust gas purifying apparatus foran engine 1, according to a first embodiment of the present invention.The engine 1 according to the present embodiment is a diesel engine, andconstitutes a driving source of a vehicle (here, a large vehicle such astruck). In the present embodiment, a reducing agent to be added to theexhaust gas from the engine 1 is stored in a liquid tank 101. Forpressure relief, this liquid tank 101 is provided with a “breatherdevice” according to the present embodiment. Moreover, in the presentembodiment, ammonia is adopted as a NOx reducing agent. However, inconsideration of simplifying use on a vehicle, a urea aqueous solutionis stored in the liquid tank 101. This urea aqueous solution is onewhere urea serving as an ammonia precursor, is previously made into anaqueous solution.

In an exhaust gas passage 2 of the engine 1, on the downstream side of amanifold part 2 a, a reducing catalytic converter 3 is disposed. The NOxin the exhaust gas is reduced and purified over this reducing catalyticconverter 3, and is then discharged into atmosphere. On the upstreamside of the reducing catalytic converter 3, there is disposed a ureaaqueous solution injecting device (corresponding to an “addition device”according to the present embodiment) 151. When the engine 1 operates,the injecting device 151 injects urea aqueous solution into the exhaustgas passage 2. Urea in the injected urea aqueous solution is hydrolyzedto readily generate ammonia serving as a reducing agent by exhaust heat.The generated ammonia efficiently reduces NOx over the reducingcatalytic converter 3, thereby converting it into harmless gas.

The urea aqueous solution is stored in the liquid tank 101, and duringactual operation of the engine, it is pressure-supplied by a feed pump(not shown in the drawing) from the liquid tank 101 into the injectingdevice 151. The injecting device 151 is connected via a urea aqueoussolution supply pipe 111 to the liquid tank 101, and the urea aqueoussolution is pressure-fed via this supply pipe 111 to the injectingdevice 151. The injecting device 151 is provided with; a main body 155that mixes the urea aqueous solution supplied from the liquid tank 101with assisting air: and an injection nozzle 156 attached at its base endside to the main body 155 and with its tip end side inserted into theexhaust gas passage 2. A tip end 156 a of the injection nozzle 156 isarranged so as to face an end face 3 a of the reducing catalyticconverter 3 on the upstream side. The injecting device 151 is connectedto the liquid tank 101 via not only the supply pipe 111 but also areturn pipe 112. Surplus urea aqueous solution supplied to the injectingdevice 151 other than that injected into the exhaust gas by theinjection nozzle 156, is returned to the liquid tank 101 via the returnpipe 112. In the injecting device 151, assisting air is supplied in acompressed state from an air tank (not shown in the drawing) to the mainbody 155. The amount of the urea aqueous solution injected by theinjecting device 151 is controlled by a control unit 201, according tothe operating state and so forth of the engine 1. In the presentembodiment, for detecting the operating state, there are provided: anaccelerator sensor 211 that detects an amount of operation of theaccelerator pedal by a driver; a crank angle sensor 212 that detects arotation angle of the crank shaft; and a temperature sensor 213 thatdetects the temperature of engine coolant, and the like. The enginerotation speed can be calculated based on the output from the crankangle sensor 212.

FIG. 2 is a plan view of the liquid tank 101 according to the presentembodiment, and FIG. 3 is a side view of the liquid tank 101. FIG. 4 isan enlarged sectional view showing a configuration of a lid part 101 aof the liquid tank 101. Hereunder is a description of a configuration ofa breather pipe 121 according to FIG. 4, with appropriate reference toFIG. 2 and FIG. 3. The breather pipe 121 constitutes a “fixing part”. Aninner pipe 122 serving as a “communication part” having afluid-communication passage therein is inserted thereinto as describedlater, to constitute the “breather device” according to the presentembodiment.

The liquid tank 101 is provided with the breather pipe 121. The breatherpipe 121, at the base end side, vertically passes through the lid part101 a of the liquid tank 101, and is fixed to the lid part 101 a. Fixingthe breather pipe 121 to the lid part 101 a is achieved, for example, bypress-fitting. In the present embodiment, in consideration of endurancewith respect to the urea aqueous solution, the breather pipe 121 is madeby forming a thin plate of stainless steel material into a cylindricalshape and joining. On one end portion of the breather pipe 121 farthestfrom the lid part 101 a, there is provided a bulging part 121 a that isexpanded outward in the radial direction. A rubber breather hose 125 isconnected to the breather pipe 121, and when the engine 1 operates,atmospheric air is introduced via the breather hose 125 and the breatherpipe 121, so that the pressure inside the liquid tank 101 is relieved.The breather hose 125 is to prevent the ingress of foreign matter fromoutside the liquid tank 101. The breather hose 125 extends along the topface of the lid part 101 a to the side of the liquid tank 101, and itsend faces downward in the vertical direction (FIG. 3). The liquid tank101 is fixed on the vehicle frame by a bracket or the like. In thedrawing (FIG. 4), the two-dot chain line U denotes a fluid level of theurea aqueous solution. The supply pipe 111 extends within the liquidtank 101 to the vicinity of the bottom, while the breather pipe 121terminates above the fluid level U, in the vicinity of the underside ofthe lid part 101 a.

FIG. 5 is a sectional view including the central axis of the breatherpipe 121, to show a configuration of a breather device A1 according tothe present embodiment, and FIG. 6 is a side view to show the inner pipe122 serving as the “communication part” of the breather device A1.

The breather device A1 is configured such that the inner pipe 122serving as the “communication part” is inserted into the breather pipe121 serving as the “fixing part”. The breather pipe 121 is made ofstainless steel as mentioned above, and for example, is press-fittedinto the lid part 101 a of the liquid tank 101 so as to provide acertain extent of fixation strength enough for securing the breatherdevice A1 to a predesigned position in the liquid tank 101. The innerpipe 122 is made of a resin, and is formed in a cylindrical shape, withan outer diameter slightly smaller than the inner diameter of thebreather pipe 121, and it has a urea aqueous solution repellentproperty. This repellent property may be an intrinsic property of theresin material. However, from a view point of preventing attachment ofthe urea aqueous solution, it is preferable that the repellent propertyis specially given by applying a repellent material coating. The innerpipe 122 is inserted concentric with the breather pipe 121, so that avent hole P of the liquid tank 101 is formed of the breather device A1.The interior of the liquid tank 101 communicates with the outside viathe vent hole P. As shown in FIG. 6, a brim part 122 a in the shape of abend is formed on the tip end (top end in FIG. 6) of the inner pipe 122,and this brim part 122 a is engaged with the bulging part 121 a of thebreather pipe 121, to thereby position the inner pipe 122 with respectto the breather pipe 121. On the outer periphery of the inner pipe 122,there is provided a plurality of projecting parts 122 b spaced apart inthe axial direction. These projecting parts 122 b are tightly engagedwith the inner surface of the breather pipe 121 to thereby fix the innerpipe 122 to the breather pipe 121 with appropriate strength. Moreover,tightly engaging of the projecting parts 122 b blocks the flow of theurea aqueous solution through the gap between the breather pipe 121 andthe inner pipe 122, thereby preventing leakage of the urea aqueoussolution from the liquid tank 101. The breather hose 125 is connected soas to cover the bulging part 121 a of the breather pipe 121 and the brimpart 122 a of the inner pipe 122. With the inner pipe 122 inserted intothe breather pipe 121, a base end 122 c projects from the breather pipe121 and extends into the liquid tank 101.

As described above, according to the present embodiment, the resin madeinner pipe 122 is inserted into the breather pipe 121 to therebyconstitute the breather device A1. By forming inner surface of thebreather device A1 that forms the vent hole P from a resin, the innersurface of the vent hole P (that is, the inner surface of the inner pipe122) is formed smooth with an appropriate repellent property. Therefore,even if sloshing occurs in the urea aqueous solution in the liquid tank101 due to vibrations or the like during traveling, and the urea aqueoussolution becomes attached to the breather device A1, it is possible toeasily drop off the attached urea aqueous solution from the breatherdevice A1 by the action of the vibrations or gravity, and return it intothe liquid tank 101. Therefore, it is possible to avoid ureaprecipitation due to the urea aqueous solution being left attached tothe breather device A1, and ensure a substantial sectional area of thevent hole P, and maintain the intrinsic pressure relief function of thebreather device A1.

As described above, the resin-coated inner surface of the vent hole P isformed by inserting a pipe member such as inner pipe 122, but theresin-coated inner surface may also be formed by coating the innersurface of the breather pipe 121 with a resin.

Hereunder is description of other embodiments of the present invention.Components or parts that correspond to those in the first embodiment aredenoted by the same reference symbols as those in FIG. 5 and FIG. 6.Also with each of the embodiments described below, an effect is obtainedwhere urea aqueous solution attached to breather devices A2 and A3 isdropped into the liquid tank 101 by the action of gravity or the like,and urea precipitation is prevented.

FIG. 7 is a sectional view showing a configuration of a breather deviceA2 according to a second embodiment of the present invention.

In the breather device A2 according to the present embodiment, theentire device is formed from a resin. That is to say, in this breatherdevice A2, the “communication part” is constituted by a cylindricalresin pipe 132, and the “fixing part” integral with the communicationpart is configured with this resin pipe 132 as a flange part 131expanded outward in the radial direction from the outer peripherythereof. The flange part 131 is fastened to the lid part 101 a of theliquid tank 101 by inserting bolts 135 into each of a plurality of boltholes provided spaced apart around the circumferential direction.Between the flange part 131 and the liquid tank 101 there is interposeda rubber O-ring 136 for ensuring air tightness of the liquid tank 101.The resin pipe 132 passes through the lid part 101 a of the liquid tank101 in the vertical direction, and projects into the liquid tank 101. Ina projecting part 132 b of the resin pipe 132 there is provided a“movable closing member” according to the present embodiment. That is tosay, in the resin pipe 132, a through-hole Ha is formed so as to passcompletely through in the axial direction, and in the projecting part132 b, the diameter of the through hole Ha expands (a portion 132 z withthis expanded diameter corresponds to the “accommodating part” of themovable body described later). On the tip end of the projecting part 132b there is provided a sectional hook shaped engaging part 132 c thatprojects inward towards the central axis of the through hole Ha. Theengaging part 132 c holds, within the projecting part 132 b, a movablebody 137 serving as a “movable closing member”. In the presentembodiment, this movable body 137 is made from a resin sphere, andwithin the projecting part 132 b, it is freely movable in the axialdirection inside the through-hole Ha of the resin pipe 132. A pluralityof holes Hb is formed passing through the side wall of the projectingpart 132 b in the radial direction. The vent hole P communicates withthe interior of the liquid tank 101 via these holes Hb in the side wall,and the through-hole Ha.

According to the present embodiment, in addition to the effects ofpreventing the urea precipitation achieved by forming the inner surfaceof the vent hole P from a resin, in particular the following effects canbe achieved. That is to say, according to the present embodiment, whenthe liquid tank 101 itself is subjected to a considerable shaking or thestored urea aqueous solution splashes and collides with the movable body137, the movable body 137 moves upward (the position after moving isshown by the two-dot chain line 137′) to thereby close the vent hole P.Therefore, ingress of the urea aqueous solution to the inside of thevent hole P can be prevented. The ventilation performance of thebreather device A2 in the normal state is ensured by the holes Hb formedin the side wall. In FIG. 7, flow of gas introduced in the normal stateis shown by the arrows F.

FIG. 8 is a sectional view showing a configuration of a breather deviceA3 according to a third embodiment of the present invention.

The breather device A3 according to the present embodiment correspondsto that of the first embodiment in that the “fixing part” is made from astainless steel cylindrical pipe (that is, a breather pipe) 121, and inthat the breather pipe 121 provides a certain extent of fixationstrength with respect to the liquid tank 101. However, it ischaracterized in that the “communication part” that forms the innersurface of the vent hole P is formed as one part 142 of the breatherhose 125 connected to the breather pipe 121. That is to say, in thepresent embodiment: the breather hose 125 is connected so as to coverthe bulging part 121 a of the breather pipe 121; and in this connectionpart, the breather hose 125 is formed in a double cylinder shape with anouter cylinder part 141 and an inner cylinder part 142; and the breatherhose 125 is connected to the breather pipe 121 by means of the outercylinder part 141, thereby ensuring air tightness of the breather deviceA3. On the other hand, the inner cylinder part 142 has an outer diameterthat is slightly smaller than the inner diameter of the breather pipe121, and is set with a length so that a tip end 142 a just projects fromthe breather pipe 121. On the outer periphery of the inner cylinder part142, there is formed a plurality of protruding parts 142 b spaced apartin the axial direction, to thereby stabilize the state of the innercylinder part 142 within the breather pipe 121. The breather hose 125 ismade of rubber, and in this sense, the “resin” in the present inventionincludes rubber.

According to the present embodiment, since the inner surface of the venthole P is formed by the inner cylinder part 142, as one portion of thebreather hose 125, there is an advantage of obtaining an effect of ureaprecipitation prevention, and an effect of improvement in the fixationstrength of the breather hose 125 to the breather pipe 121 at the sametime, while reducing the number of components.

In the foregoing description, only selected embodiments have been chosento illustrate the present invention. However, the scope of the presentinvention is not limited by this description, but is to be interpretedbased on the appended claims in accordance with to applied articles.

1. A breather device configured to be disposed in a liquid tank forstoring urea aqueous solution, comprising: a fixing part configured toprovide the breather device with fixation strength enough for securingthe breather device to the liquid tank, wherein the fixing part isformed by joining a plate of stainless steel material into a cylindricalshape with a hollow extending therethrough in an axial direction; and abreather tube comprising a communication part joined to the fixing part,the communication part configured to form therein a vent hole forproviding fluid communication between an interior of the liquid tank andan outside thereof, wherein in the communication part, an inner surfaceof the vent hole is formed from a resin, wherein the breather tube isattached to one end of an outside of the liquid tank to form therein agas-flow passage communicatable with the vent hole, and wherein thecommunication part permits one end of the breather tube to be formed toextend into the inside of the fixing part.
 2. The breather deviceaccording to claim 1, wherein the communication part protrudes furtherbeyond an end face of the fixing part on a side in the vicinity of aninterior of the liquid tank into the interior.
 3. The liquid tankcomprising: a tank main body configured to store therein a liquid; andthe breather device according to claim 1, which is attached to the tankmain body.
 4. An exhaust gas purifying apparatus for an enginecomprising: a reducing catalytic converter provided in an exhaust gaspassage of the engine; the liquid tank according to claim 3, which isconfigured to be appropriate for storing ammonia or its precursor in anaqueous solution state; and an addition device configured to add theammonia solution or precursor solution stored in the liquid tank to anexhaust gas at a position upstream of the reducing catalytic converter.